Při kopírování hierarchických dat zachovejte vztahy rodiče a potomka

CTE funguje dobře s MERGE , ale je problematický v SQL Server 2005. Omlouváme se za zavádějící komentář dříve.

Následující text ukazuje, jak klonovat projekt (s více stromy) a opravit rodičovství, aby se oddělila nová doménová struktura od staré. Všimněte si, že nezávisí na žádném konkrétním uspořádání ID, např. nemusí být husté, monotónně se zvětšující, ... .

-- Sample data.
declare @Projects as Table
  ( Id Int Identity, ProjectId Int, Value VarChar(16), ParentId Int Null );
insert into @Projects ( ProjectId, Value, ParentId ) values
  ( 611, 'Animal', 0 ),
  ( 611, 'Frog', 1 ),
  ( 611, 'Cow', 1 ),
  ( 611, 'Jersey Cow', 3 ),
  ( 611, 'Plant', 0 ),
  ( 611, 'Tree', 5 ),
  ( 611, 'Oak', 6 );
-- Display the raw data.
select * from @Projects;

-- Display the forest.
with IndentedProjects ( Id, ProjectId, Value, ParentId, Level, Path ) as
  ( -- Start with the top level rows.
  select Id, ProjectId, Value, ParentId, 0, Convert( VarChar(1024), Right( '000' + Convert( VarChar(4), Id ), 4 ) )
    from @Projects
    where ParentId = 0
  union all
  -- Add the children one level at a time.
  select P.Id, P.ProjectId, P.Value, P.ParentId, IP.Level + 1, Convert( VarChar(1024), IP.Path + '<' + Right( '000' + Convert( VarChar(4), P.Id ), 4 ) )
    from IndentedProjects as IP inner join
      @Projects as P on P.ParentId = IP.Id
  )
  select Space( Level * 2 ) + Value as [IndentedValue], Id, ProjectId, Value, ParentId, Level, Path
    from IndentedProjects
    order by Path;

-- Clone the project.
declare @OldProjectId as Int = 611;
declare @NewProjectId as Int = 42;
declare @Fixups as Table ( OldId Int, [NewId] Int );
begin transaction -- With suitable isolation since the hierarchy will be invalid until we apply the fixups!
insert into @Projects
  output Inserted.ParentId, Inserted.Id
    into @Fixups
  select @NewProjectId, Value, Id -- Note that we save the old Id in the new ParentId.
    from @Projects as P
    where ProjectId = @OldProjectId;
-- Apply the fixups.
update PNew
  set ParentId = IsNull( FNew.[NewId], 0 )
  -- Output the fixups just to show what is going on.
  output Deleted.Id, Deleted.ParentId as [ParentIdBeforeFixup], Inserted.ParentId as [ParentIdAfterFixup]
  from @Fixups as F inner join
    @Projects as PNew on PNew.Id = F.[NewId] inner join -- Rows we need to fix.
    @Fixups as FOld on FOld.OldId = PNew.ParentId inner join
    @Projects as POld on POld.Id = FOld.OldId left outer join
    @Fixups as FNew on FNew.OldId = POld.ParentId;
commit transaction;

-- Display the forest.
with IndentedProjects ( Id, ProjectId, Value, ParentId, Level, Path ) as
  ( -- Start with the top level rows.
  select Id, ProjectId, Value, ParentId, 0, Convert( VarChar(1024), Right( '000' + Convert( VarChar(4), Id ), 4 ) )
    from @Projects
    where ParentId =0
  union all
  -- Add the children one level at a time.
  select P.Id, P.ProjectId, P.Value, P.ParentId, IP.Level + 1, Convert( VarChar(1024), IP.Path + '<' + Right( '000' + Convert( VarChar(4), P.Id ), 4 ) )
    from IndentedProjects as IP inner join
      @Projects as P on P.ParentId = IP.Id
  )
  select Space( Level * 2 ) + Value as [IndentedValue], Id, ProjectId, Value, ParentId, Level, Path
    from IndentedProjects
    order by Path;